Adipocyte-specific loss of PPARγ attenuates cardiac hypertrophy

Adipose tissue is a key endocrine organ that governs systemic homeostasis. PPAR gamma is a master regulator of adipose tissue signaling that plays an essential role in insulin sensitivity, making it an important therapeutic target. The selective PPAR gamma agonist rosiglitazone (RSG) has been used to treat diabetes. However, adverse cardiovascular effects have seriously hindered its clinical application. Experimental models have revealed that PPAR gamma activation increases cardiac hypertrophy. RSG stimulates cardiac hypertrophy and oxidative stress in cardiomyocyte-specific PPAR gamma knockout mice, implying that RSG might stimulate cardiac hypertrophy independently of cardiomyocyte PPAR gamma. However, candidate cell types responsible for RSG-induced cardiomyocyte hypertrophy remain unexplored. Utilizing cocultures of adipocytes and cardiomyocytes, we found that stimulation of PPAR gamma signaling in adipocytes increased miR-200a expression and secretion. Delivery of miR-200a in adipocyte-derived exosomes to cardiomyocytes resulted in decreased TSC1 and subsequent mTOR activation, leading to cardiomyocyte hypertrophy. Treatment with an antagomir to miR-200a blunted this hypertrophic response in cardiomyocytes. In vivo, specific ablation of PPAR gamma in adipocytes was sufficient to blunt hypertrophy induced by RSG treatment. By delineating mechanisms by which RSG elicits cardiac hypertrophy, we have identified pathways that mediate the crosstalk between adipocytes and cardiomyocytes to regulate cardiac remodeling.